1. Field of the Invention
The present invention relates to a semiconductor element test apparatus which brings a plurality of probe needles into contact with semiconductor elements fabricated on a semiconductor wafer, as well as to a method of testing a semiconductor element.
2. Background Art
Processes for manufacturing a semiconductor integrated circuit, such as an IC or an LSI, include a test process generally called a wafer test process. As shown in FIG. 8, during the course of a wafer test process, there is employed a semiconductor element test device which brings a plurality of probe needles 7 of a probe card 1 attached to a wafer prober 2 into contact with semiconductor elements fabricated on a semiconductor wafer 5 placed on top of a stage 4. As shown in FIG. 8, the wafer prober 2 is provided with a test head 10, and the test head 10 is connected, by way of a cable 15, to a tester 3 constituted of a computer.
As shown in FIG. 9, the test apparatus performs a test as to whether or not semiconductor elements 6 are non-defective, through the following steps. Namely, the probe needles 7 are brought into contact with respective electrode pads 8 of a plurality of semiconductor elements 6 (i.e., semiconductor chips) fabricated on the semiconductor wafer 5. In this state, an electrical test input signal is sent to the semiconductor elements 6 from the tester 3 by way of the cable 15 and the probe needles 7. A test output signal processed by the semiconductor elements 6 is sent back to the tester 3 by way of the probe needles 7 and the cable 15. FIG. 10 shows a state of contact between the probe needles 7 and the electrode pads 8. The stage 4 is pushed up toward the probe needles 7 during a test, and the electrode pads 8 are brought into contact with the probe needles 7. After completion of the test, the stage 4 is lowered, thereby separating the electrode pads 8 from the probe needles 7.
FIG. 11 is a side view showing the constitution of the prober 2 while the stage 4 remains in a lowered position. FIG. 12 is a perspective view showing a probe card 1 having the probe needles 7 mounted thereon. FIG. 13 is a top view showing the probe card 1. The prober 2 is equipped with the probe card 1. The probe card 1 has a probe card substrate 12 which supports the plurality of probe needles 7. The prober 2 has a test head 10 which operates in cooperation with the probe card 12. A plurality of probe needles 7 are supported on the lower surface of the probe card substrate 12, and on the top of the probe card substrate 12 are provided a reinforcement member 13 for reinforcing the probe card substrate 12, and a plurality of ZIF connectors 11. A plurality of ZIF sockets 9 corresponding to ZIF connectors 11 are provided on the lower surface of the test head 10. The semiconductor elements 6 exchange a test input signal and test output signals with the tester 3, by means of the ZIF connectors 11 being coupled to the ZIF sockets 9. The ZIF sockets 9 incorporate springs and are connected to the ZIF connectors 11 by means of meshing action.
As shown in FIG. 14, the probe card substrate 12 is attached to a probe card hold member 26 along with the reinforcement member 13. As shown in FIG. 15, screws 17 are used for attaching the probe card substrate 12 and the reinforcement member 13. As shown in FIG. 15, the wafer prober 2 is provided with the probe card hold member 26, and the probe card hold member 26 is attached to a movable arm 27. The probe card hold member 26 is used in transporting the probe card 1 into the wafer prober 2 or in transporting the probe card 1 outside the wafer prober 2. The probe card hold member 26 is used for fixing the probe card 1 within the prober 2. The probe card hold member 26 is formed into a ring, and the probe card substrate 12 of the probe card 1 is attached to the probe card hold member 26 with the reinforcement member 13 such that the probe needles 7 protrude from an opening of the ring-shaped probe card hold member 26. As shown in FIG. 16, the probe card 1 is held so as to protrude from an opening 25 formed in an top of the prober 2 while being attached to the probe card hold member 26. The probe card 1 is positioned by means of positioning pins 14 of the test head 10. In this state, the probe card 1 opposes the semiconductor wafer 5 provided on top of the stage 4 with a predetermined space therebetween.
In the related-art apparatus using the screws 17, when a test is performed, the stage 4 is elevated, thereby pressing the semiconductor wafer 5 against the probe needles 7. At this time, stress concentrates at the portions of the probe card substrate 12 where the reinforcement member 13 is attached by means of the screws 17, as a result of which load is imposed so as to induce warpage in the probe card 1. Accordingly, warpage partially develops in the probe card substrate 12. When the probe card 1 has been used over a long period of time, the tip ends of the probe needles 7 become offset from their initial locations. Uniform contact between the probe needles 7 and the semiconductor elements 6 is not sustained. As a result, contact failures arise in some of the semiconductor elements 6, such that non-defective elements 6 may be determined to be defective.
In order to prevent occurrence of warpage in the probe card substrate 12, which would otherwise arise while the probe card substrate 12 is in use, the reinforcement member 13 constituted of a flat plate of hard material is used, as shown in FIG. 17. A structure for attaching the reinforcement member 13 to the probe card substrate 12 and to the probe card hold member 26 is specifically shown in FIG. 18. Counterbores 13a to be used for attaching the screws 17 are formed in two attachment arms 13A and 13C from among four attachment arms 13A through 13D of the reinforcement member 13. In contrast, no counterbores 13a are formed in the remaining two attachment arms 13B and 13D. Thus, the attachment structure is not uniform. such a non-uniform attachment structure is ascribable to the positioning pins 14 of the test head 10. In order to avoid the positioning pins 14, the counterbores 13a are formed in only the attachment arms 13A and 13C. However, the attachment structure is not uniform and fails to sufficiently prevent occurrence of warpage in the probe card substrate 12. Reference numeral 16 designates a through hole through which the attachment screws 17 penetrate.
The test head 10 is a housing in which a plurality of terminals are provided in a concentrated manner for connecting the tester 3 with the probe card 1. As shown in FIGS. 15 and 16, the test head 10 is provided on top of the wafer prober 2 in a reclosable manner. The positioning pins 14 of the test head 10 are provided for enabling the test head 10, the probe card 1, and the wafer prober 2 to be connected together at the same positions at all times. Positioning holes 21 (see FIG. 16) formed in the probe card substrate 12 are located close to the edges of the attachment arms 13A and 13C. Hence, the counterbores 13a are formed in only the attachment arms 13A and 13C.
As shown in FIG. 18, because of such a non-uniform attachment structure, short screws 17 are used for the attachment arms 13A and 13C, and long screws 17 are used for the attachment arms 13B and 13D. The difference in length between the screws 17 also accounts for occurrence of warpage in the probe card substrate 12. Use of two types of screws 17 having different lengths makes attachment and removal of the screws 17 complicated, thus resulting in consumption of excessive time.
When the probe needles 7 are brought into contact with the electrode pads 8 of the semiconductor element 6 under normal conditions, the stage 4 is elevated so as to scrub the surface of the electrode pads 8 after the probe needles 7 have been brought into contact with the electrode pads 8, so as to eliminate an oxide film which naturally arises in the surface of the electrode pads 8. During repetition of a wafer test, insulating material adheres to the tip ends of the probe needles 7, resulting in an increase in contact resistance. As a result, non-defective semiconductor elements 6 are determined to be defective, thereby undesirably deteriorating manufacturing yield of semiconductor elements. In order to prevent such deterioration, abrasion and cleaning of the tip ends of the probe needles 7 is periodically performed. In order to inspect the positional accuracy of the probe needles and the abrasion and cleaning state of the probe needles 7, the probe card substrate 12 is removed from the probe card hold member 26 in conjunction with the reinforcement member 13, by means of removing the screws 17. After inspection, the probe card substrate 12 must be attached again to the probe card hold member 26.
Use of the two types of screws renders attachment and removal of the screws complicated, thereby lengthening working time. As shown in FIGS. 19A and 19B, flat-head screws having flat heads 17A are used as the screws 17. The flat-head screws have shallow slots 17a to be used for rotating screws, and the slots 17a are easily collapsed. Attachment and removal of the screws 17 is performed often, and therefore the screws 17 must be replaced with new ones. Rust-resistant, hard stainless screws have hitherto been used for the screws 17. However, such screws cannot be magnetically attracted to a driver, which deteriorates workability.
The present invention proposes a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member and can reduce warpage in the probe card substrate.
Further, the present invention proposes a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member and can reduce warpage in a probe card substrate by means of realizing commonality of screws used for attaching the probe card reinforcement member.
Further, the present invention proposes a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member, reduces warpage in a probe card substrate, and enables frequent replacement of screws by means of improving mount screws.
Further, the present invention proposes a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member, reduces warpage in a probe card substrate, and facilitates attachment and removal of screws by means of improving mount screws.
Further, the present invention proposes a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member and reduces warpage in a probe card substrate by means of improving the reinforcement member so as to increase the reinforcement strength thereof.
Further, the present invention proposes a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member and reduces warpage in a probe card substrate, by means of increasing the fastening strength acting between the reinforcement member and the probe card substrate.
Further, the present invention proposes a semiconductor element test method which prevents undesirable deterioration in manufacturing yield of semiconductor elements, through use of a semiconductor element test apparatus which improves a structure for attaching a probe card reinforcement member to a probe card hold member and can reduce warpage in a probe card substrate.
According to one aspect of the present invention, a semiconductor element test apparatus comprises a stage on which a semiconductor wafer having semiconductor elements mounted thereon, and a probe card having a plurality of probe needles opposing the semiconductor wafer, and the semiconductor elements are tested by means of bringing the plurality of probe needles into contact with the semiconductor elements of the semiconductor wafer. The probe card has a probe card substrate for supporting the plurality of probe needles and a reinforcement member to be used with the probe card substrate. The semiconductor element test apparatus has a probe card hold member. The probe card substrate is attached to the probe card hold member in a plurality of mount positions, by means of screws and by way of the reinforcement member. Counterbores of substantially the same depth and shape are formed in respective mount positions on the reinforcement member. The probe card substrate is attached to the probe card hold member by means of the screws and by way of the counterbores.
According to another aspect of the present invention, in a method of testing a semiconductor element uses a test apparatus which brings a plurality of probe needles provided on a probe card into contact with semiconductor elements of a semiconductor wafer. The probe card has a probe card substrate for supporting the plurality of probe needles, and a reinforcement member to be used with the probe card substrate. The semiconductor element test apparatus has a probe card hold member having the probe card attached thereto. The reinforcement member is attached to the probe card substrate and to the probe card hold member at a plurality of mount positions, by means of screws. Counterbores of substantially the same depth and shape are formed in the respective mount positions on the reinforcement member. The probe card substrate is attached to the probe card hold member by means of the screws and by way of the counterbores.
Other and further objects, features and advantages of the invention will appear more fully from the following description.